This is the first application filed for the present invention.
Not applicable.
The present invention relates to voice communications systems, and, in particular, to a method and apparatus for enabling the interworking of broadband networks that use dissimilar protocols to provide telephony services.
Modem telecommunications systems have evolved with and around the Public Switched Telephone Network (PSTN) and the Common Channel Signaling (CCS) network. Although the PSTN is an integrated, highly reliable network that is well adapted for voice service, it is expensive to construct and maintain. Furthermore, the bandwidth capacity of the circuit-switched PSTN is limited to 64 kb/s per circuit and any unused capacity of a circuit cannot be shared. The steady increase in demand for telecommunications services has taxed resources in the PSTN. Consequently, packet networks, which offer higher bandwidth capacity and resource sharing have been adapted for use in supplementing the PSTN. Recent telecommunications system configurations have incorporated Asynchronous Transfer Mode (ATM) and/or Internet Protocol (IP) networks for payload transport, with interfaces to the circuit-switched PSTN. ATM and IP networks that perform payload transport are referred to as broadband transport networks.
As the use of broadband transport networks has increased to satisfy the demand for telecommunications services, so has the number of interfaces to the PSTN. Each transport network has an associated set of transport protocols that govern the format of data units transferred through the network. Generally, a protocol data unit (PDU) for one transport protocol cannot be transferred through a transport or telephone network that uses a different transport protocol. For this reason, edge-connecting two or more broadband transport networks, and expanding addressing capabilities of respective network elements, does not necessarily enable the interworking of the two or more networks. Two networks are said to interwork when the content of PDUs of one of the two networks can be forwarded through the other of the two networks, and vice versa, and can be processed by edge equipment. Generally, an interface is provided between the two networks that performs a protocol conversion without loosing or corrupting payload data. Several such interfaces have been developed to permit the interworking of the PSTN with various broadband networks. Examples of such devices are described in Applicant""s co-pending U.S. patent application Ser. Nos. 09/158,855 which was filed on Sep. 23, 1998 and is entitled TRANSIT TRUNK SUBNETWORK; and, 09/213,769 which was filed on Dec. 17, 1998 and is entitled METHOD AND APPARATUS FOR COMPLETING TELEPHONE CALLS BETWEEN SUBNETS.
Since interfaces to the PSTN exist for some broadband transport networks, it is common to provide interworking between incompatible broadband networks by routing through the PSTN. Consequently, each of the broadband transport networks interwork with the CCS network to convey call control messaging, and each is edge connected to the PSTN. However, using the PSTN as a bridge between broadband transport networks is inefficient as each conversion back and forth from packet to PSTN results in additional transmission delays and requires more equipment.
Accordingly, a method and apparatus that enables the direct interworking of different broadband transport networks for the provision of telephone services remains highly desirable.
An object of the present invention is to provide a method and apparatus for direct interworking of broadband transport networks.
Accordingly, the invention provides an apparatus for inter-working among broadband transport networks that employ dissimilar transport protocols. The apparatus comprises an Interworking Gateway (IWG). The IWG provides adaptation from any one to any other of a provisioned set of transport protocols, in response to control messaging, and signaling associated with respective networks. This interface between the broadband transport networks permits direct interworking between the broadband transport networks.
Independence of transport protocol adapters of an IWG is assured by the use of the base signal format in the design of the IWG. The IWG is comprised of a set of bi-directional interfaces, ports for example, to respective broadband networks. Each bi-directional interface is connected to at least one receive path and at least one transmit path. The receive path converts incoming PDUs (from the connected interface) into the base signal format. Each transmit path converts base signal format data into PDUs conforming to the transport protocol associated with its interface. A set of connected receive paths, transmit paths and one or more bi-directional interfaces may therefore be removed, inserted or modified independently from the other connected sets in the IWG without affecting the functioning of any of the other connected sets in the IWG. The IWG comprises a switch that connects/disconnects transmit paths to/from receive paths, and a controller of the switch and other components of the IWG. The switch controller of the IWG is adapted to exchange signaling with Call Servers of each of the broadband networks to which it has an interface.